Creating custom capabilities…??

Been struggling with this for 2 days now, and can’t seem to find a way round it or a plugin that claims to provide this functionality.

Basically I’m trying to set up a video gallery/submission page on my site (it’ll – hopefully – be fully tabbed like the images page with each tab displaying a different event, and each tab has it’s own upload form). At the moment I’m using Contact Form 7’s upload form as after several months of searching I’ve not found a plugin or even a suitable hack (that I’m able to reproduce myself) that allows front-end video uploading – except for a few that provide video comment functionality, one of which I’m already using – nor have I found a suitable video gallery plugin.

So in the meantime I’d prefer to prevent just anyone from accessing the upload form and limit it to subscribers and higher. Does anyone know how to create custom capabilities for uploading specific file types? I’m using Role Manager for roles/capabilities…